(The Center Square) – There are no cheap solutions for fixing or eliminating the damaged high rise section of the West Seattle Bridge, the Seattle Department of Transportation reports.
In an 89-page analysis released on Tuesday, the department laid out five potential options the city could pursue to get the 36-year-old commuter bridge back in shape or replace it outright.
The bridge acted as the primary connection between West Seattle and the rest of the city up until its closure in March after inspectors found signs of cracking along its underside during a route inspection. SDOT officials anticipate it could be closed until at least 2022.
Each option was analyzed based on not only initial construction costs, but the price of long-term maintenance and community impact.
One option would repair the bridge’s cracked sections for about $50 million in initial costs and be completed in two years, SDOT officials estimated. Operations and maintenance costs would go for around $22.1 million over 79 years.
The SDOT analysis notes that repairing the bridge would likely incur the shortest closure and impact businesses and low-income commuters the least.
Another option would replace the bridge’s high rise section with another concrete structure and would cost around $380 million, the analysis found, but cost only $22.1 million to maintain and operate. This option would take until at least 2026.
On Wednesday, HNTB Corp engineer Ted Zoli proposed a new high rise section with twin steel spans which he estimated would be 40% lighter and more resilient than the current concrete main span. It could be completed by 2023.
Between repairing or replacing the bridge’s cracked high rise, the former would see the city rack up more than $1.2 billion in eventual repairs versus the $247.3 million in repair costs in the latter scenario.
Analysts warned that because of Seattle’s insufficient bridge funding, costly repairs to the West Seattle Bridge may come at the cost of additional SDOT transportation projects.
A third option would shore up the bridge’s damaged high rise section with additional support structures. This option was rated as a poor option by SDOT officials.
According to the analysis, a fourth option would be to replace the entire West Seattle bridge, which SDOT estimated would provide the greatest safety from earthquakes.
The fifth and most expensive option would be replacing the bridge with a $1.9 billion immersed-tube tunnel.
SDOT officials wrote that repairing or replacing the high rise structure “rise to the top” of the options listed in its analysis.
The top lines of the analysis were prepared by WSP, a consulting firm and longtime partner of SDOT.
Replacing part or all of the West Seattle bridge would also not be able to accommodate Sound Transit’s planned light rail extension in 2032, the analysis found.
Seattle's Community Task Force is expected to finalize their recommendations in the coming weeks along with the Technical Advisory Panel. SDOT will also submit its recommendations.
Seattle Mayor Jenny Durkan is expected to make her recommendation sometime next month.